1. Field of the Invention
The present invention relates to adhesive compositions suitable for anchoring or fixing elements in a base or structural body, and to methods of anchoring. More specifically, the present invention is directed towards adhesive compositions and methods that are especially well suited for curing such compositions at lower temperatures, without compromising desirable characteristics such as strength and durability.
2. Discussion of the Related Art
It is well known that adhesive systems are useful for fixing or anchoring materials in or to rock, masonry, and concrete. Such systems typically involve the use of synthetic resins and monomers that are maintained separately from a hardening or curing agent until they are combined at or near the point of fastening. A variety of additional and often optional adjuvants may also be used with adhesive systems.
By way of example, U.S. Pat. No. 5,157,072 to Hense, et al., teaches ethylenically unsaturated, substituted cycloaliphatic compounds as monomers and resins for minimizing shrinkage of the adhesive when used for anchoring bolts in bore holes. However, Hense, et al., is silent on low shrinkage stress. U.S. Pat. No. 5,288,767 to Cramer, et al., teaches a methacrylate monomer in the first component together with diluent monomers. One of the stated goals of this patent is to eliminate styrene as a comonomer, but Cramer, et al., is silent on the subject of low-temperature curing. U.S. Pat. No. 6,037,408 to Weber, et al., is similar to the Cramer '767 patent, but it requires the use of very high levels of monomer and is silent on the affects of low temperature cure. Variously, U.S. Pat. No. 6,583,259, Weber, et al., is concerned with adhesives to bond to wet bore holes; U.S. Pat. No. 7,544,739, to Liu, et al. teaches a composition for use under conditions of elevated temperatures; and U.S. Pat. No. 5,077,324 to Kistner, et al., is concerned with extending the shelf life the formulation prior to use. Neither any of the foregoing, nor a great many other references are directed towards adhesive compositions that are suitable for curing at low temperatures.
It is often the case that adhesives must be applied to anchoring elements in concrete and masonry under adverse weather conditions involving low temperatures and/or excess moisture. Unfortunately, it is not until the arrival of warmer weather at some later point in time that weakness or failure of the anchoring elements are observed. The effects of warming the substrate have been largely ignored in the past. Often, products that are developed for cold environments make the assumption that the substrate will not warm appreciably. Another tactic that has often been employed is to produce multiple variations of a product where several closely related compositions are developed, each associated with a specific temperature range. Under new protocols, however, the costs for testing can be prohibitive for a product line with multiple adhesives.